A fine pattern of 30 nm or less is required for microfabricated high-density recording media such as next-generation semiconductor devices or patterned media. It is difficult to form such a fine pattern by current lithography techniques. A method of forming a fine pattern at lower cost and high throughput is proposed (see, for example, Japanese Patent No. 3926360 and JP-A 2009-57519 (KOKAI)). In the method, a fine pattern is formed using a microphase-separated structure by self-assembly of a block copolymer containing a mesogenic group.
As the thickness of such a block copolymer film is smaller, defect numbers and size variations after pattern transfer to the substrate are reduced. Consequently, a thin film with a thickness of 50 nm or less is considered to be desirable. However, when the thickness is set to 50 nm or less, the arrangement becomes random and the microphase-separated structure cannot be obtained.